On This Day: A paper by David Brewster is read to the Royal Society, belatedly announcing his discovery of what w

1/15 (1818): A paper by David Brewster is read to the Royal Society, belatedly announcing his discovery of what we now call the biaxial class of doubly-refracting crystals. On the same day, Augustin-Jean Fresnel signs a "supplement" (submitted four days later) on reflection of polarized light.